1. Field of the Invention
The present invention relates to an obstacle detecting system for a motor vehicle for detecting an object or obstacle such as typified by a car running ahead or in front of the motor vehicle.
2. Description of Related Art
As a obstacle detecting system for a motor vehicle of the type mentioned above and known heretofore, there have been proposed and developed those systems which are based on a laser radar type distance detecting (or ranging) technique and a stereoscopic (or binocular) video camera technique. By way of example, an obstacle detecting system which adopts the laser radar type distance detecting or ranging method is disclosed in Japanese Patent Publications Nos. 6473/1991 and 30117/1991. In these known obstacle detecting systems, a flat laser beam diverging vertically in a sector-like shape is deflected from the left to the right and vice versa in a direction laterally transversely to the direction in which the motor vehicle equipped with the obstacle detecting system is running, for thereby detecting the distance to an object such a car running ahead as well as the width thereof on the basis of the difference between a time point at which the laser beam is emitted and a time point at which an echo beam is received.
On the other hand, an obstacle detecting system for a motor vehicle implemented by using a stereoscopic video camera unit is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 161810/1992 (JP-A-4-161810). In the case of this known obstacle detecting system, a pair of optical systems such as video cameras or the like are disposed at the front side of a motor vehicle in a vertical or horizontal array with a predetermined distance between them, wherein the images of an object such as a car running ahead or an obstacle existing in front which are picked up by the optical systems are focused onto a pair of image sensors. By comparing the video signals outputted from the image sensors after photoelectric conversion and representing the images focused onto the image sensors, deviation between the images on the image sensors is detected, whereon distance to the object is arithmetically determined in accordance with the principle underlying the trigonometric measurement which per se is known.
The hitherto known obstacle detecting systems for a motor vehicle mentioned above however suffer from problems, which will be elucidated below.
With the obstacle detecting system implemented by using the laser radar type distance detecting apparatus, it is only the distance to a car running ahead or an obstacle existing in front and the width thereof that can be detected, because of such arrangement that the flat laser beam of the shape mentioned previously is deflected to the left and right or laterally transversely relative to the direction in which the motor vehicle equipped with the obstacle detecting system is running.
On the other hand, in the case of the obstacle detecting system implemented by using the stereoscopic video camera apparatus, it is only the presence of an object such as an obstacle and the distance thereto that can be detected because the useful information is derived by processing the images of the object picked up through a pair of optical systems in accordance with the trigonometrical measurement principle.
As can be seen from the above, with the obstacle detecting system for a motor vehicle known heretofore, the detection information available is only of the distance to a car running ahead or an obstacle existing in front and the width thereof. It is impossible to obtain information concerning the height of the object. In other words, the amount of information available from the known obstacle detecting system is not sufficient for optimizing the running control of the motor vehicle with high reliability.
Besides, when a fault takes place in the obstacle detecting system constituted solely either by the laser radar type distance detecting apparatus or the stereoscopic video camera apparatus, there arises such situation that the information concerning the object or obstacle existing in front can not be obtained at all, giving rise to another problem.